def _eval_subs(self, old, new):
        # keep processing of power-like args centralized in Pow
        if old.is_Pow:  # handle (exp(3*log(x))).subs(x**2, z) -> z**(3/2)
            old = exp(old.exp * log(old.base))
        elif old is S.Exp1 and new.is_Function:
            old = exp
        if old.func is exp or old is S.Exp1:
            f = lambda a: Pow(*a.as_base_exp(), evaluate=False) if (a.is_Pow or a.func is exp) else a
            return Pow._eval_subs(f(self), f(old), new)

        if old is exp and not new.is_Function:
            return new ** self.exp._subs(old, new)
        return Function._eval_subs(self, old, new)

 def _eval_power(self, other):
     """exp(arg)**e -> exp(arg*e) if assumptions allow it.
     """
     b, e = self.as_base_exp()
     return Pow._eval_power(Pow(b, e, evaluate=False), other)